Sulfur-aided aerobic biostabilization of swine manure and sawdust mixture: Humification and carbon loss

Combining citrus waste-derived function microbes with biochar promotes humus formation by enhancing lignocellulose degradation in citrus waste compost

The low degradation rate of lignocellulose limits the humification process of citrus organic waste composting. This study explored the roles of general microbial inoculation (GM), citrus waste-derived function microbial inoculation (CM), and CM combined with biochar (CMB) in citrus waste compost. Results showed microbial inoculations all promoted lignocellulose degradation and humus formation, but the roles of CM and CMB were better than GM, especially CMB. Compared to the control, CMB raised the temperature and duration of thermophilic phase by 2.8 °C and 4 days, and improved lignin degradation rate and humus content by 21.5% and 7.6%. Furthermore, CMB promoted bacterial community succession and cooperation, and decreased network complexity. Moreover, CMB strengthened the correlation between mainly bacterial communities and polysaccharides, reducing sugars as well as carbohydrates metabolic, enhancing the contribution of bacteria such as Bacillus, Flavobacterium and Staphylococcus to humus and its precursors. It concludes that the naturally derived microbes in compost had better effects on promoting humus synthesis than exogenous microbes, which provides a new route for rapid humification of high-lignin organic waste in composting.

The bioaugmentation effect of microbial inoculants on humic acid formation during co-composting of bagasse and cow manure

The effective degradation of recalcitrant lignocellulose has emerged as a bottleneck for the humification of compost, and strategies are required to improve the efficiency of bagasse composting. Bioaugmentation is a promising method for promoting compost maturation and improving the quality of final compost. In this study, the bioaugmentation effects of microbial inoculants on humic acid (HA) formation during lignocellulosic composting were explored. In the inoculated group, the maximum temperature was increased to 72.5 °C, and the phenol-protein condensation and Maillard humification pathways were enhanced, thus increasing the HA content by 43.85%. After inoculation, the intensity of the microbial community interactions increased, particularly for fungi (1.4-fold). Macrogenomic analysis revealed that inoculation enriched thermophilic bacteria and lignocellulose-degrading fungi and increased the activity of carbohydrate-active enzymes and related metabolic functions, which effectively disrupted the recalcitrant structure of lignocellulose to achieve a high humification degree. Spearman correlation analysis indicated that Stappia of the Proteobacteria phylum, Ilumatobacter of the Actinomycetes phylum, and eleven genera of Ascomycota were the main HA producers. This study provides new ideas for bagasse treatment and recycling and realizing the comprehensive use of resources.

The biotic effects of lignite on humic acid components conversion during chicken manure composting

Targeted regulation of composting to convert organic matter into humic acid (HA) holds significant importance in compost quality. Owing to its low carbon content, chicken manure compost often requires carbon supplements to promote the humification progress. The addition of lignite can increase HA content through biotic pathways, however, its structure was not explored. The Parallel factor analysis revealed that lignite can significantly increase the complexity of highly humified components. The lignite addition improved phenol oxidase activity, particularly laccase, during the thermophilic and cooling phases. The abundance and transformation functions of core bacteria also indicated that lignite addition can influence the activity of microbial transformation of HA components. The structural equation model further confirmed that lignite addition had a direct and indirect impact on enhancing the complexity of HA components through core bacteria and phenol oxidase. Therefore, lignite addition can improve HA structure complexity during composting through biotic pathways.